Code Compare is a free compare tool designed to compare and merge differing files and folders. Code Compare integrates with all popular source control systems: TFS, SVN, Git, Mercurial, and Perforce. Code Compare is shipped both as a standalone file diff tool and a Visual Studio extension.
Beyond Compare - Beyond Compare allows you to compare files and folders.
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.
Araxis Merge - Home of the award-winning Araxis Merge two and three-way file comparison (diff) and merging application, Araxis Find Duplicate Files, Araxis Replace In Files, and the Araxis Ketura issue tracking, project scheduling and time tracking application.
DiffMerge - DiffMerge is a graphical file comparison program for Windows, Mac OS X and Unix, published by...
P4Merge - A valuable tool for diagnosing continuous integration bugs, Folder Diff also measures how much code must be resolved in pending merge scenarios. Visually compare two versions using image diff within P4Merge to determine changes made.